Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$147.95	11.872%	$165.5146	$165.51	$165.50	$165.50
Purchase #2	$240.41	13.245%	$272.2523	$272.25	$272.25	$272.30
Purchase #3	$60.70	4.114%	$63.1972	$63.20	$63.20	$63.20
Purchase #4	$92.86	11.746%	$103.7673	$103.77	$103.75	$103.80
Purchase #5	$210.77	5.103%	$221.5256	$221.53	$221.55	$221.50
Purchase #6	$192.63	11.807%	$215.3738	$215.37	$215.35	$215.40
Purchase #7	$49.74	8.874%	$54.1539	$54.15	$54.15	$54.20
7 purchase totals =	$995.06		$1,095.7847	$1,095.78	$1,095.75	$1,095.90